The Energy of Interaction between Two Acetone Molecules:  A Potential Function Constructed from ab Initio Data

Abstract

An analytical function representing the energy of interaction in the acetone dimer was constructed on the basis of ab initio (MP2/6-31+G*) calculations for 327 configurations. The inclusion of electron correlation in the ab initio calculations was essential for satisfactory reproduction of experimental data, as was the avoidance of basis set superposition error by means of the counterpoise method. The analytical potential function was fitted to the ab initio data using a weighting scheme favoring good fit in low-energy regions. The minimum of the function, −4.83 kcal/mol, corresponds to a C 2 h symmetry in which the monomers are antiparallel and are linked by four hydrogen bonds. Three low-energy stationary points corresponding to transition states with differing numbers of hydrogen bonds and energy were also located. The quality of the function was corroborated by inspection of derived isoenergetic contour maps and of its prediction for the temperature dependence of the second virial coefficient. As a further test, a Monte Carlo simulation of liquid acetone was performed in the canonical ensemble, and energetic properties and radial distribution functions were computed.